This invention relates generally to a high power cable and method for the production of such continuous sheathed cable. Specifically, the invention is directed to a method for producing continuous sheathed cable that will not transmit gas or vapors and, accordingly, is usable in corrosive or explosive ambient environments.
This is an improvement on U.S. patent applications Ser. Nos. 083,538 filed Oct. 10, 1979, issued May 26, 1981 as U.S. Pat. No. 4,269,638; 083,414 (abandoned); and 083,540 filed Oct. 10, 1979, issued June 2, 1981 as U.S. Pat. No. 4,270,961 assigned to the assignee hereof.
The improved method permits the continuous production of sheathed cable utilizing a pliable, inert sealing material and annular corrugations to prevent passage of gases or vapors along the cable core. The composite cable formed by the instant methodology includes an insulated and often jacketed conductor or conductor ensemble, an outer metal corrugated sheath, and a layer of pliable sealing material wrapped with tape disposed between the conductor assembly and the outer metallic sheath. The improved method includes extruding or pumping a layer of sealing compound around the insulated conductor, wrapping the sealing compound with flexible tape, forming a sealed metallic sheath around the composite assembly, and corrugating the outer metallic sheath to compress the sealing compound and fill the space between the inner and outer members thereby forming an air-tight seal. The sealing compound may be continuously or periodically applied along the length of the cable.
Many national and local building and electrical codes require sealed, sheathed cable to meet rigorous standards with regard to the transmission of gases or vapors through the core of the cable. One such standard is set out in the National Electrical Code promulgated by the National Fire Protection Association at Article 501, Paragraph (e) (2) which limits gas or vapor flow through a cable to a maximum of 0.007 cubic feet per hour of air at a pressure of 6 inches of water. The sheathed cable produced by the improved method of the present invention fully meets the National Electrical Code standard.
Accordingly, it is an object of this invention to provide an improved continuous sheathed cable and method for its production.
It is another object of this invention to provide an improved method for producing sheathed cable which is impervious to the passage of gas or vapors.
It is another object of this invention to provide an improved method for producing sheathed cable utilizing a pliable sealing compound and annular corrugations.
These and other objects, features, and advantages of the invention will be better understood by reference to the following drawings read in conjunction with the detailed description of illustrative embodiments to follow.